U.S. patent application Ser. No. 06/879,886, filed June 30, 1986 discloses a device for coupling, under safe conditions, one end of a drug delivering small tube to an apparatus for coupling a syringe to the drug holding bottle. This device has a free end (that is, its end which is to be coupled to the mentioned apparatus) which has substantially the form of a body shaped as the mouth of a conventional bottle of the type used for holding a drug. From the shaped body three or more longitudinal fins project. The fins have an even flat longitudinal outer profile and operate for assuring an axial insertion of the above-mentioned free end of the device and a firm holding of the device in the seat of the apparatus whereon the drug holding syringe is mounted.
As stated in the above mentioned patent application, the apparatus to be coupled to the syringe is provided with three or more resilient lugs each of which bears a tooth which, as the free end of the device is inserted into the apparatus seat, engages under the free edge of the device. Such an apparatus is disclosed in U.S. Pat. No. 4,576,211.
It has been found that the provision of the longitudinal fins projecting from the body (and the radially outermost longitudinal peripheral edge of which is even) may cause latching problems if the longitudinal fins are arranged in front of the teeth of the flexible or resilient lugs of the apparatus. In fact, if the device is not arranged with its fins disengaged from the resilient lug teeth of the apparatus, then the device can not be coupled to the apparatus. Moreover, the user may not notice the drawback, with the very dangerous consequence (it should be remembered that many drugs are very toxic) that the device may detach from the apparatus during the drug delivering step.